Due to their high energy densities, car makers forced the development of lithium-ion batteries for hybrid-electrical vehicles. High charge and discharge pulses heat up a lithium-ion battery, which could lead to accelerated battery degradation, (loss of capacity), or even a safety-critical defect. This book deals with the design of a temperature and current depending switching strategy of a high- voltage electrical system, consisting of a lithium- ion battery and a double-layer capacitor. For the validation of the proposed controlling concept the models are integrated into a complete vehicle simulation of the hybrid power train using an independent co-simulation environment. This book emphasizes the capabilities of a co-simulation environment for vehicle developers and engineers.